1. Field of the Invention
The present invention relates generally to a high-speed packet data communication system, and in particular, to a method and apparatus for receiving interleaved data and deinterleaving the received interleaved data into its original data format.
2. Description of the Related Art
A Code Division Multiple Access (CDMA) mobile communication system, for example, a CDMA IS-2000 system and a Universal Mobile Telecommunication Service (UMTS) Wideband CDMA (WCDMA) system, supports both a voice service and a circuit data service.
A synchronous CDMA2000 Release A/B mobile communication system and an asynchronous UMTS mobile communication system employ turbo coding and interleaving for reliable transmission of multimedia data. It is well known that turbo coding provides a very high information restoration capability in view of a bit error rate (BER) even at a low signal-to-noise ratio (SNR), and interleaving prevents defective bits in a fading environment from concentrating on one point. The interleaving allows adjacent bits to randomly undergo fading effects to prevent a burst error, thereby contributing to an increase in channel coding effects.
To meet increasing demand for a service requiring high-speed packet data transmission, such as the Internet and moving image services, a mobile communication system tends to develop into a system supporting a high-speed packet data service. According to CDMA2000 Release C/D, known as Evolution in Data and Voice (1xEV-DV) standard, driven by Third Generation Partnership Project (3GPP) and Third Generation Partnership Project 2 (3GPP2), a base station segments code symbols generated by encoding a transmission packet data stream by a channel encoder into subblocks with a predetermined size, and interleaves the respective segmented subblocks. A mobile station receives a stream of the interleaved subblocks, converts the received subblock stream into code symbols, and performs deinterleaving, a reverse operation of interleaving used in the base station, on the code symbols, to thereby restore the received subblock stream into the original signal output from the channel encoder.
In the CDMA2000 Release A/B standard, a length of a code symbol stream which becomes the subject of interleaving must be divided by a power of 2. That is, it is provided that a length of a code symbol stream should become a multiple of a number having 2 as its base and having a bit shift value, one of interleaving parameters, as its exponent. On the contrary, in 1xEV-DV, a length of a subblock code symbol stream is not divided by a power of 2. That is, the 1xEV-DV standard defines an interleaving rule different from that of the existing standards. Hence, the 1xEV-DV standard needs technologies for enabling a mobile station to receive a data stream interleaved according to the new interleaving rule and rapidly effectively deinterleave the received data stream.